There has been known an electro-photographic type image forming apparatus including a plurality of toner cartridges and a plurality of drum cartridges. The toner cartridges separately accommodate toner of yellow color, toner of magenta color, toner of cyan color, and toner of black color. Each of the plurality of toner cartridges is attachable to and detachable from the corresponding one of the plurality of drum cartridges. The toner cartridge is attachable to a main body of the image forming apparatus in a state where the toner cartridge is attached to the corresponding drum cartridge. This type of image forming apparatus is disclosed in, for example, the prior art.